Thread by @FirstDoctor

This disease affects mainly the eyes & skin. It's caused by worms transmitted through the bite of infected black flies.

ONCHOCERCIASIS is the 2nd leading infectious cause of blindness globally but many people know nothing about it.

A thread 🧵

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The black fly which causes onchocerciasis breeds mainly in fast-flowing rivers & streams.

This happens mainly in remote villages in the tropics located near fertile lands where people rely heavily on farming or herding.

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The female adult worms produce #larvae (microfilariae) that migrate to the skin, eyes & other organs.

One female worm can release up to 1000 larvae a day into surrounding tissue.

The worms can live up to 15 years in the human body enclosed in fibrous tissues called #nodules.

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When a female black fly bites an infected person during a blood meal, it also takes in the larvae.

These larvae then evolve into the infectious stage & are transmitted to the next human host during the next bite.

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When the microfilarial worm dies, it induces inflammatory reactions that cause;

- intense itching
- bumps under the skin
- skin scarring
- skin swelling
- loss of skin elasticity (e.g. hanging groin)
- total loss of skin color (leopard skin) & sometimes
- total blindness

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Onchocerciasis can be treated with a drug called #ivermectin.

This drug paralysis the worms, reduces their production of more larvae, & reduces the itching & progression to blindness.

You must take this drug at least once yearly for 10-15 years for treatment to be complete.

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To prevent onchocerciasis, avoid black fly bites;

🔸use insecticides that contain DEET (diethylmetatoluamide) on exposed skin

🔸wear long sleeve shirts & trousers

🔸wear permethrin treated clothes

No vaccine or approved drug to prevent the disease, so avoid black fly bites